Method of and means for indicating paper dryness



METHOD OF AND MEANS FOR INDICATING PAPER DRYNESS Filed May 28, 1930 Slljnpa e I4 I [9 4/ 22 J; 28 25 I u I I I I I I 24 4 If /6 INVENTOR Step/zen A. Szfizeye AA WM ATTORNEY Patented Oct. 25, 1932 UNITED STATES PATENT OFFICE STEPHEN A. STAEGE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE .ELECTRIO & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA METHOD OF AND MEANS FOR IN DICATING PAPER DBYNESS Application filed May 28, 1930. Serial No. 456,781.

My invention relates to indicators and particularly to indicators for indicating the amount of moisture in a moving web of fibrous material.

An object of my invention is to provide a relatively simple, compact and easily operated device for indicating the amount of moisture in a web of fibrous material, such as paper.

-Another object of my invention is to provide a dryness indicator which depends for its operation on the principle that fr1ct1on between a solid surface and a moving web of paper increases with an increase in the moisture content of the web.

Another object of my invention is to rovide a paper-dryness indicator which s all indicate the average moisture content of a web of paper integrated laterally of the web.

In practicing my invention, I provide a roll which is positioned in operative engagement with one surface of a moving web of fibrous material, such as paper, with a predetermined and adjustable pressure therebetween, and driven by suitable means at such speed that its peripheral speed is substantially different from the speed of travel of the web of paper so that the slippage therebetween will be above the critical slippage oint.

Suitable indicating means is provided in combination with the roll-driving means, which may be an electric motor, in order to indicate the amount of friction and, therefore the amount of moisturein the moving web.

In the single sheet of drawing, Figure 1 is a view, in side elevation, of

' the dry end of a paper dryer and a set of calender rolls having a device embodying my invention associated therewith.

Fig. 2 is a top plan view of the parts shown in Fig. 1,

Fig. 3 is a diagram of connections of an electric circuit associated with the device embodying my invention, and,

Fig. 4 is a curve showing the relation between the slippage between surfaces in frictional engagement and the friction of motion therebetween.

I have shown only the last few of a plurality of steam dryer drums 11- which may be of the kind utilized for drying a moving web of fibrous material '12, such "as paper, the dryer drums being rotatably supported in side frames 13 and 14, in a manner well known in the art.

A steam header 16 is provided at one side of the set of dryer drums and a second header 17 is located at the other side of the set, suitable pipe connections 18 being provided between the header 16 and one end of the dryer drums to provide for a substantially continu-' ous supply of fresh or live steam to the drums. Similar pipes 19 are provided between the other ends of the drums and the header 17 to permit of the condensed steam flowing out of the drums. The connections between the headers 16 and 17 and the drums 11 may be made in any suitable or desired manner, as is well understood in the art.

While I have not shown the wet end of the paper machine, it is to be understood that such device is provided and has prepared the initially wet web of paper which is then threaded around and over the plurality of steam drums 11 to be dried thereon and to then pass through and over a plurality of calender rolls 21 mounted in, and supported by, suitable end frames 22 and 23. The calender rolls, their supports, and the end frames 22 and 23 are shown generally only as they constitute no part of my invention.

The web 12 is wound on a reel stand 24, in a manner well known in the art. A tensioning roll 26 is provided between the final drier drum 11 and the set of calender rolls 21 and I have indicated that it is pivotally and yieldingly supported from the frames 13 and 14 by arms 27 and 28. Here, also, I have shown particular elements or deatils for illustrative purposes only, as these elements constitute no part of my invention.

It is highly desirable that the operator supervising the work of the paper machine should have a substantially continuous indi-( moisture content of the web of paper as it leaves the d.?er rolls. I wish to state here that, while shall describe the device and system embodying my invention as a means for indicating the degree of dryin or the moisture content of a moving web 0 fibrous material, it is also within the province of my invention to thereby control the amount of heat supplied to the dryer rolls and to thus maintain -the moisture content of the moving web of paper within relatively narrow limits. 4

The device and system embodying my invention includes, more particularly, a roll 31 that is rotatably supported in suitablebearing members which are located in the ends of two arms 32 and 33 which are pivotally supported atv the sides of the web of paper and more particularly by the side frames 22 and 23 of the calender rolls. The arms 32- and 33 are pivotally supported, intermediate their ends on suitable brackets 34 and 36, counterweights 37 and 38 being adjustably mounted on the other ends of the arms to permit of obtaining a predetermined and .adjust-able pressure between the roll 31 and one surfaice of the moving web of fibrous ma.- ter1a I desire to efiect rotation ofthe roll 31 at such speed that its peripheral speed shall be substantially different from the speed of travel of the web 12 and, for this purpose, I provide a dynamo-electric machine 41 to be suitably mounted on a bracket 42 which is secured to the arm 33, in substantially the manner shown in Figs. 1 and 2 of the draw- The roll 31 is provided with a shaft 43 that extends therethrough and has. a pulley .44 of suitable size mounted thereon at one end and immediately beneath the motor 41, the shaft of which is provided with a pulley 46 to drive the roll 31 by a suitable belt 47 ex tending around the pulleys 44 and 46.

I have shown a dryer-driving motor 51 operatively connected to one or more of the dryer drums, as by a chain or belt 52, it being understood, however, that the mechanical connection between the motor 51 and the dryer drums is shown schematically only for illustrative purposes.

An electric system operatively associated with the paper machine which includes the hereinbefore described dryer drums, comprises a generator 53 driven by any suitable prime mover and providing direct-current electrical energy.

The motor 51 is a direct-current motor and is energized from generator 53 through a plurality of conductors 54, all in a manner well known in the art. I have illustrated the motor 41 schematically in Fig. 3 of the drawing as comprising armature 55, a field winding 56, and an ad ustable field rheostat 57.

The motor 41 may be started by any suitable known means and may be so controlled, as to its speed, that the peripheral speed of the roll 31 will be a predetermined amount below or above the speed of travel of the web 12. This can easily be effected by adjustment of the field rheostat 57, and it may be noted that the peripheral speed of roll 31 may be made greater than the speed of travelof the web 12 byincluding a greater portion of the resistance of rheostat 57 in circuit with the field winding .56 to weaken the field strength of motor 41. In this case, the roll 31 will move faster than'does the web 12, and the motor 41 will operate as a motor and draw current from generator 53. If the field of motor 41 be made sufliciently strong by means of increasing the field current by cutting out more of rheostat 57, its speed will tend to decrease, and the peripheral speed of roll 31 will be less than the speed of travel of the web 12 so that machine 41 will operate as a generator and tend to return current to machine 53.

In order to obtain an indication of the value of the current traversing the armature of motor 41, I provide an indicator 60 including a suitable current-traversed winding or coil 61 having associated therewith a movable electro-magnet core 62, which actuates a suitable pivotally mounted pointer 63, tl1e outer end of which moves over a suitably graduated scale 64. The scale 64 may be calibrated in units of coefficient of friction between the surface of the roll and the web of paper or, if preferred, it may be calibrated directly in terms of moisture content of the web of paper, such as in percent moisture content. (This instrument may be some standard form'of ammeter or other indicating or recording instrument, the latter instrument permitting of obtaining a permanent record.) It may here be stated that, in general, the percentage content of moisture of a moving web of paper, such as newsprint, should not exceed, say 9% to 10% and should possibly be a few percent below this maximum value.

I have hereinbefore stated that the difference in speed between the surface of the roll 31 and that of the moving web of fibrous material should preferably be such that the slippage therebetween is above the critical slippage point in the transmission of power between the moving web of fibrous material and the particular kind of material ofwhich the roll 31 is made. While I believe that it is possible to use any one of a number of different kinds of material for the roll 31, I have used a roll made of aluminum and have found that I canobtain consistent indications of the true moisture content ofthe web of paper. Experiments have also been made in the use of wood, phenolic condensation products, glass, porcelain and other materials and consistent results have been obtained as to the moisture content.

lid

I have found that the relation between the including,

across, and in operative engagement e full width of the web of paper. My

friction of motion and the amount of slippage between two relatively moving coo rating surfaces, such as a roll and a web 0 fibrous material, when the'roll is made of one of the above named materials, isas shown in curve 66 of Fig.4 with a predetermined ressure therebetween. The friction increases initially as the slippage increases and thereafter decreases if the slippage is still further increased. The slippage at which the maximum friction is experienced I have termed the critical slippage point. This point is represented at the hump ofcurve 66 in F ig. 4, in which the abscissae represent slippage, and

the ordinates L represent the friction of'motion between the roller and the paper web.

The shape of this curve will vary with variations in the cooperating materials and in the pressure therebetween and the curve is therefore, relative rather than absolute. found it preferable to operate the roll 31 at such rotative speed that the slippage between its surface and the paper or web of fibrous ma- I terial is above the critical point, or stated in another way, I prefer to operate on the drooping part of the slip-coefficient or friction curve. I have found that the friction of motion between a roll of this kind and a web of fibrous material will vary greatly when the difference in speed between the frictionally engaging surfaces is low or small and below the critical point of curve 66, but I have also found that, when this difi'erenceof speed of travel is large and above the critical point of the curve shown in Fig. 4, the friction becomes a more stable quantity and is not affect- I ed, to any great extent, by varying amounts of slippage.

Stated in another way, if the roll 31 is operated at such peripheral speed as to be below the critical point of curve 66, the system will be in an unstable and highlyundesirable con dition. If the cooperating pressure be a predetermined value and if the difference in speeds be such as to bring the slippage below the critical value and if the percentage of moisture in the paper increases suddenly, then the coefiicient of friction will also correspondingly increase, and the slippage will tend to increase, thereby making the entire indicating system and device 'very unstable. If however, the indicating system embodying my invention is operated at a point above the critical value indicated in Fig. 4, and if the moisture content suddenly increases the corresponding increase in the c'oeflicient of friction will cause such ,decrease in the slippage that the device and the system become quite stable in their operation.

It may be noted that the device embodying my invention provides a relatively simple and easily operated means for obtaining an indication of the percentage of moisture content of a moving web of fibrous material,

I have,

more particularly, a roll extending entirel with, th device provides also means for obtaining a predetermined amount of pressure between the roll and the moving web of paper so that any desired or required adjustments may be easily and quickly made.

The arms 32 and 33 are so supported that they extend substantially parallel to the moving web of paper, whereby the pressure between the roll and the web will remain at the predetermined value, as determined by the position of the weights 37 and 38, irrespective of the variations in the web tension. Thus,

may happen that the speed of the reel-driving mechanism will varyslightly, thereby varying the tension in the web. If the position of the roll were fixed, the friction be tween it and the web would vary, and any indication of the moisture content would be in error. However, with the roll supported as shown, the. roll pressure is independent of the web tension and the readings of the indicator will be affected to a negllgible degree only by momentary slight variations in.the tension of the web.

As the dynamo-electric machine 41 is electrically connected to the source of supply providing the energy for driving the dryer, it is obvious that the indicator will not be affected by a change in the speed of travel of the web, which change in speed may be necessary at times. If the system, including ,more particularly the dynamo-electric machine 41, the roll 31 and the indicator 60, has once been adjusted, so that there is a predetermined difference in speed between the web and the roll surface, the armature current of machine 41 is an indication of the moisture current (or dryness) of the web, regardless of the actual paper speed. When once the roll speed has been adjusted for a predetermined percentage above or below the paper speed, the predetermined percentage difference will be maintained, regardless of changes in the paper speed, so that the indicator will give correct readings with different paper speeds.

Actual tests on a device having substantially the construction hereinbefore described, have shown that substantially correct indications of the percentage of moisture content of a moving web of fibrous material, such as paper, can be obtained and that the mechanism will continue to operate for relatively long periods of time without requiring an appreciable amount of attention.

Various modifications may be made in the device and system embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or set forth in the appended claims.

I web and measuring the va ue of the friction resisting motion between the web and the roll in terms of moisture content.

2. The method 'of determining the mois-- tu're content of a moving web of fibrous'ma-. terial which comprises the steps of rotatin a roll in frictional engagement with sai web at a peripheral s eed differing from the speed of the web an measuring the power required to drive the roll in terms of moisture content.

3. The method of determining the moisture content of a moving web of fibrous ma-' terial which includes the steps of rotating a roll in frictional sliding engagement wit the web at a predetermined pressure therebetween and measuring the value of the moisture content as a function of the power required to drive the roll.

4. The method of determining the moisture content of a moving web of fibrous material which includes the steps of rotating a roll in frictional engagement with the web at a predetermined pressureh therebetween and at a peripheral speed differing from the speed of the moving web and measuring the value of the moisture content as a function of the friction resisting motion between the web and the roll.

5. The method of determining the moisture content of a moving web of fibrous material which includes the steps of rotating a roll in frictional engagement with the web at a predetermined pressure therebetween independent of the web tension and at a peripheral speed differing from the speed of the web-t such extent that the slippage therebetween is above the critical slippage point of the cooperating surfaces and measuring the value of the moisture content as a function of the friction resisting motion therebetween.

. 6. The method of determining the moisture content of a moving web of fibrous material which includes the steps of rotating a roll in frictional engagement with the web at a peripheral speed that is higher than the speed of the web to such extent that the slippage therebetween is above the critical slippage point of the cooperating surfaces and measuring the value of the moisture content as a function of the friction resisting motiontherebetween. v 7. The method of determining the moisture content of a moving web of'paper which includes the steps of rotating a roll in frictional engagement with the web at a predetermined pressure therebetween and at a peripheral speed differing from the speed of the moving web, causing the roll to follow minor movements of the web at its point of engageripheral speed differing from the speed of the web and current responsive indicating means actuated by the armature current of the dynamo-electric machine for measuring the moisture content of the paper.

9. In a paper-dryness indicating system for indicating the moisture content of a moving web, a roll, means for maintaining the roll in frictional engagement with the moving web, current-traversed electric means for rotating said roll at aperipheral speed differing from the speed of travel of the web, and a current responsive indicating device actuated by the current traversing the electric means for measuring the molsture content of the paper.

In testimony whereof, I have hereunto subscribed my name this 21st day of May, 1930.

c STEPHEN A. STAEGE. 

